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Office 365 PST import

I'm doing a PST import to Office 365 using azcopy and the PST mapping file.

I ran into some problems in the beginning and a mailbox only got imported about 30%.

If i start the import proces again, will it replace the emails already being in the mailbox?
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Vasil Michev (MVP)
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Thanks for the answer. I tested it with a small mailbox and it does not seem to make duplicates.

Is there also a way to make the upload for the PST go faster? It seems like azcopy is only using 25% of my upload speed.
If you experience slower than expected upload speed you use to determine blob storage latency from your location.

If you are importing into multiple mailboxes, simply use multiple instances, each with different admin account.

Best time to do this over the weekend, when there is not much load on the online service overall.

Also get help from this article for uploading PST files to Exchange Online using Microsoft Azure Storage.

Hope this helps!

The following methods will help you to resolve your issue:

1. Transfer the PST file to OWA account via Drive Shipping method.

Follow the given steps to upload the file:
  • Copy the MS Outlook PST files to a BitLocker-encrypted hard disk.
  • Now, physically ship the hard drive to Microsoft.
  • Microsoft  will upload the received Outlook PST database in the cloud of Microsoft.
  • You can use the Outlook 365 import service and migrate the PST to Exchange Online.

2. Export Outlook PST files to Office 365 account via Network Upload.
Follow these steps for this solution:
1. Copy SAS URLinstall Azure AzCopy.
2. Transfer Outlook PST files to O365.
3. View the entire list of uploaded Outlook Data files.
4. Create PST Import Mapping file.
5. Create PST Import Job.
To know more about these solutions in detail, visit the following link:

3. You can also try a reliable third-party service to import PST to Office 365.

Best Regards,
Tej Pratap Shukla
Vasil Michev gave the answer. The upload speed was just the cause of a slow internet connection.